We prospectively collected data on the signs, symptoms, and physical findings in over 2,000 patients having computed tomography of the head in our tertiary care teaching hospital. We correlated these data with the results of CT in an attempt to determine whether we could identify any evidence for inappropriate utilization of cranial CT for diagnostic purposes. If we examined only patients whose presenting complaints were statistically more often seen in patients with abnormal CT's compared to normal CT's, we would have eliminated 26 percent of all examinations but would have missed 18 percent of all abnormal patients. Similarly, if we examined only patients thought by their physician to have a high likelihood of intracranial disease or to be a diagnostic dilemma, we would have eliminated 34 percent of all examinations and 26 percent of all abnormals. We found no way of separating normal from abnormal patients.